Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Avalanches in wind-drifted snow will be the most likely problem, and conditions may be challenging due to shifting wind directions. Steer around steep terrain below ridgelines and on cross-loaded slopes. Avoid steep north aspects, especially north and east of Mazama, where there is still a chance of triggering a very large, consequential avalanche on old snow layers. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Older wind slabs are gaining strength, but fresh wind drifting could form shallow new slabs on Wednesday. After numerous days of westerly wind, winds shift southeast on Wednesday. The most likely place to trigger a wind slab is steep, unsupported slopes at upper elevations, especially in confined gullies. Look for blowing snow and cornices, and feel for stiffer snow layers beneath the surface. Cracks shooting out from your equipment or recent avalanches are signs to avoid steep terrain. You can also use small wind-affected test slopes to observe how the snow reacts. If the snow fractures and slides easily, you could trigger an avalanche on a larger slope. 

    A smaller wind slab might step down to more deeply buried weak layers, becomingg a very large and dangerous avalanche. 

    (11/26/2024)

    Example of shooting cracks in wind-textured snow. 

    Photo: Will Govus

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    With this low likelihood, high consequence situation, continue avoiding steep northerly slopes where you could trigger one of these very large avalanches. They may be easier to trigger near exposed rocks or on wind-loaded slopes. Persistent slabs take a long time to gain strength and require patience along with careful decision-making. 

    We expect this problem to be more likely further north and east in the forecast area. But with significant uncertainty, it's best to focus on the potential consequences and continue to travel conservatively. You may not receive any of the typical warning signs, like collapsing before triggering a slide, and these avalanches could be unsurvivable, breaking across entire slopes and running long distances.  In two separate involvements in late February near Harts Pass, snowmobilers were buried, and one person was killed. More recently, observers in this area found test results showing that the weak layer still has the potential to fail and propagate. Further east, near Tiffany Mountain, an observer reported widespread collapsing and recent large, widely propagating avalanches.

    (3/17/2025)

    A widely propagating avalanche near Tiffany Mtn.

    Photo: Willie Webster

Avalanche Discussion

On Wednesday, winds are expected to shift southeasterly, and light snow may favor the eastern mountains. Recent storm totals near Washington Pass range from 1 to 2 feet, but taper quickly further east in the zone. In the past week, observers have reported natural and triggered small wind slabs at upper elevations. On March 17, an observer near Tiffany Mountain reported widely propagating recent natural avalanches and rolling collapses on a weak layer in the middle to lower half of the snowpack.

A late February storm brought 18" of snow to the area and was followed by prolonged warm weather into early March. From February 23rd to at least March 3rd, this resulted in multiple widespread natural avalanche cycles, starting with persistent slabs and then wet loose and wet slab avalanches. Observers reported many large to very large avalanches with widely propagating crowns. The weak layer (January Drought Layer) is buried 2–3.5 ft (70-120cm) below the surface near Washington Pass, but shallower further east and north. Near Rainy and Easy Passes, the JDL is over 4 feet deep and capped with a thick melt-freeze crust. In many parts of the zone, it's become difficult to trigger this weak layer. On March 12th, observers near Harts Pass reported large and small column tests indicating that, if triggered, propagation is still likely. We believe persistent slab avalanches are still possible in areas with a shallow and weaker snowpack in the north and eastern parts of the zone.

NWAC Forecasters visited the site of the avalanche fatality near Harts Pass that occurred on 2/28. You can read the initial observation here. 

You can help us gather more data by submitting an observation HERE or via the Avy App. 

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